[1/2] Add get_next_strinfo helper function

[Richard Sandiford]

This patch just adds a helper function for getting the next strinfo
in a chain, since part 2 adds another place where we do that.

Tested on aarch64-linux-gnu and x86_64-linux-gnu.  OK to install?

Thanks,
Richard


2017-05-16  Richard Sandiford  <richard.sandif...@linaro.org>

gcc/
        * tree-ssa-strlen.c (get_next_strinfo): New function.
        (get_stridx_plus_constant): Use it.
        (zero_length_string): Likewise.
        (adjust_related_strinfos): Likewise.
        (adjust_last_stmt): Likewise.

Index: gcc/tree-ssa-strlen.c
===================================================================
--- gcc/tree-ssa-strlen.c       2017-05-15 19:57:18.899053381 +0100
+++ gcc/tree-ssa-strlen.c       2017-05-15 20:50:21.412511763 +0100
@@ -156,6 +156,19 @@ get_strinfo (int idx)
   return (*stridx_to_strinfo)[idx];
 }
 
+/* Get the next strinfo in the chain after SI, or null if none.  */
+
+static inline strinfo *
+get_next_strinfo (strinfo *si)
+{
+  if (si->next == 0)
+    return NULL;
+  strinfo *nextsi = get_strinfo (si->next);
+  if (nextsi == NULL || nextsi->first != si->first || nextsi->prev != si->idx)
+    return NULL;
+  return nextsi;
+}
+
 /* Helper function for get_stridx.  */
 
 static int
@@ -665,10 +678,8 @@ get_stridx_plus_constant (strinfo *bases
   gcc_checking_assert (compare_tree_int (si->length, off) != -1);
   for (chainsi = si; chainsi->next; chainsi = si)
     {
-      si = get_strinfo (chainsi->next);
+      si = get_next_strinfo (chainsi);
       if (si == NULL
-         || si->first != chainsi->first
-         || si->prev != chainsi->idx
          || si->length == NULL_TREE
          || TREE_CODE (si->length) != INTEGER_CST)
        break;
@@ -736,26 +747,18 @@ zero_length_string (tree ptr, strinfo *c
       si = verify_related_strinfos (chainsi);
       if (si)
        {
-         chainsi = si;
-         for (; chainsi->next; chainsi = si)
+         do
            {
-             if (chainsi->endptr == NULL_TREE)
+             gcc_assert (si->length || si->stmt);
+             if (si->endptr == NULL_TREE)
                {
-                 chainsi = unshare_strinfo (chainsi);
-                 chainsi->endptr = ptr;
+                 si = unshare_strinfo (si);
+                 si->endptr = ptr;
                }
-             si = get_strinfo (chainsi->next);
-             if (si == NULL
-                 || si->first != chainsi->first
-                 || si->prev != chainsi->idx)
-               break;
-           }
-         gcc_assert (chainsi->length || chainsi->stmt);
-         if (chainsi->endptr == NULL_TREE)
-           {
-             chainsi = unshare_strinfo (chainsi);
-             chainsi->endptr = ptr;
+             chainsi = si;
+             si = get_next_strinfo (si);
            }
+         while (si != NULL);
          if (chainsi->length && integer_zerop (chainsi->length))
            {
              if (chainsi->next)
@@ -833,12 +836,8 @@ adjust_related_strinfos (location_t loc,
          si->endptr = NULL_TREE;
          si->dont_invalidate = true;
        }
-      if (si->next == 0)
-       return;
-      nsi = get_strinfo (si->next);
-      if (nsi == NULL
-         || nsi->first != si->first
-         || nsi->prev != si->idx)
+      nsi = get_next_strinfo (si);
+      if (nsi == NULL)
        return;
       si = nsi;
     }
@@ -995,15 +994,9 @@ adjust_last_stmt (strinfo *si, gimple *s
        return;
       while (firstsi != lastsi)
        {
-         strinfo *nextsi;
-         if (firstsi->next == 0)
-           return;
-         nextsi = get_strinfo (firstsi->next);
-         if (nextsi == NULL
-             || nextsi->prev != firstsi->idx
-             || nextsi->first != si->first)
+         firstsi = get_next_strinfo (firstsi);
+         if (firstsi == NULL)
            return;
-         firstsi = nextsi;
        }
     }